Preservation of rubber



" UNIT-BMW troducjed, through contamination during the processingoi the rubber. Ithas been proposed Patented June 2 1942 ES PAT J azsazsa rnasaava'rion or ems;

Frederick B. Downing, Carney: Point, N. 1., Ar-

thin-1M. ,Neal, Wilmington, Del., and Charles]. Pedersen, Penna Grove, N; 1., assignors to E. I. du Pont de Nemonrs 8: Company, Wilmington,

Del., a corporation oi Delaware I Application December N0. 182,374

-45 (c1. act-[892):

No Drawing,

,This invention relates to the preservation of rubber, particularly in the presence oi j copper and its compounds whichcatalyze the deterioration oi. rubberdueto the action of heat and oxi- It is well knownthat certain substances, for

increase the rate of deterioration due to heat and oxidation several hundred percent. This great catalytic activity of copper necessitates expensive and tedious processes to; insure that all copper is removed, from compounding agents. It is alsofnecessary to be sure jthatno copper is inheretofore" to overcome this catalytic action ,throughthe use of well known antioxidants such as phenylb-naphthylamine." Such "compounds,

however, are relativelyinefiective in overcoming the catalytic action of the copper.

An objectof thepres ent invention is to provide anew classofcornpounds whichare effective in overcomingthe catalytic action of copper on that deterioration which rubber normally undergoes due totheaction of heat and oxidation. 1 A furlther object is to retard the deterioration of rubher due to heat and oxidationevenin the presence of copper and itscompounds which normally accelerate such deterioration. A still iurther object is to render the usual rubber antioxidants 'eflective even in the presence of copper and its compounds in the presence of which such antioxidants are usually relatively ineffective- Other objects aretoprovidenewTcompositions of matter and to advance the art. Still other obj ects will appear hereinafter.

These objects may be accomplished in accordance with our invention which comprises incorpo'rating inthe rubber a small amount of an organic compound containing an ortho-hydroxy aromatic group and a tertiary. nitrogen having two moles of a an ortho-hydroxy substitutedfalde hyde" which is aromaticin nature, so that not more than one mole of aldehyde reacts for each primary amino group of the amine. l

A The polyamine may be any aliphatic amine ntaining at least ,twoprimary amino groups directly attached a; different carbon atoms of a the same open chain and which amine may contain aromatic or other cyclicgroups substituted on the chain; The .term aliphatic polyamine" as employed hereinafterand in the claims willbe understood to have the foregoing meaning. The

polyamine may be "an aromatic or other cyclic amine having at least two'primary amino groups attached to different substantially adjacent atoms oi the ring or rings, either directly or through one or more atoms which arenot members otthe rings. The preferredpolyamines are those consisting at carbon, hydrogen and nitrogen,ythose in which at least two primary amino groups are directly attached to adiacentcarbon atoms, and particularly the diamines.

By substantially adjacent atoms, we mean only ring atoms directly bonded together and ring atoms located indiflerent nuclei of polynuclear compounds which ring atoms are the two two valencies satisfied by a single carbon atom x and asmallamount oi a rubber antioxidant or a diflerent type.

The organic compound above reierredto is a type of arylidene amine or Schifl's base,.obtained by condensing one mole of c a. polyamine, containing at least two primary aminofgroups capable oi reacting with aromatic aldehydes to form arylidene amineswith at least atomswnot common to two rings nor forming part or the linkagebetween two rings, nearestgto each other. By "adjacent atoms," we mean at oms directlybonded together. By polynuclear compounds," we mean to include compounds containing two or morerings having no'ringcarbon atoms in common as well as fused ringcompounds.

By an forthdhydrosy substituted aldehyde,"

we mean one in which the hydroxy groupand the aldehyde, or --CHO, group are directly bonded ,to adjacent ring carbonatoms. By the term aldehyde, aromatic in nature? we intend to include the unsaturated cyclic aldehydes, such as the pyridine and quinoline aldehydes, which have many of the characteristic properties of the aromatic aldehydeaas well as the strictly aromatic aldehydes in which the hydroxy and aldehyde groups are bonded to nuclear carbon atoms of an m aromatic ring'.

The aldehyde is preferably an aromatic aldehyde and alsolpreierably one devoid of substituents other than hydrocarbon and hydroxy groups; However, such aldehyde may contain, as substituents, alko w, yloxy, halogen, heterocyclic, amino, cyano, carboxyl and sultonic groupsas well as hydrctinalkyl and ary1 radi-' cals, it The polyamine may belikewise substituted 65 butispreierablyunsubstituted. a

ENT OFFICE c Compounds of this type are well known and methods of making them are described by Mason, Ber. 20 267-277 (1887) and Haegele Ber. 25 2753-2756 (1892). They are further discussed by N. U. Sidgwick in his books The Electronic Theory of valency Oxford 1927 and The C- valent Link in Chemistry, Cornell 1933.

The above compounds are, in general, relatively ineffective in retarding that deterioration which 'rubber undergoes due to heat and oxidation, in the absence of metal catalysts, and hence they are not valuable commercially as antioxidants. However, we have found that, when such compounds are employed in rubber and in the presence of an antioxidant of a diiferent type, they tend to inhibit or neutralize the catalytic efl ct of copper and its compounds, and hence are hereinafter named copper deactivators, for convenience. In inhibiting the deterioration of rubber due to heat and oxidation the usual antioxidants are substantially ineffective in the presence of .copper and its compounds when such antioxidants are employed alone. Our compounds, when employed alone, have little if any, preservative effect on, rubber whether in the presence or absence of copper and its compounds.

The quantity of copper deactivator added will be dependent upon the amount of copper present in the'rubber. At least one mole of copper deactivator must be added for each atom of copper in the rubber. Preferably, from about 1.5 to

' Y about 100 moles of copper deactivator is used for each atom of copper in the rubber. From about 0.0002to about 1.0% of copper deaetivator based on the rubber will generally be satisfactory in most rubber compositions where the copper or its compound is accidentally present. Higher ratios of copper deactlvator may be used, particularly when the rubber is in contact with metallic copper in bulkwhich forms a reservoir of copper ions.

In order to test these compounds, the following stocks were prepared.

A B C D E Lithopone 2o 20 20 20 20 Dl-ortho tolyl guauidine" 0. 75 0. 75. 0. 75 0. 75 0. 75

Phenyl-b-naphthylamine. 1. 00 l. 00 l. 00 l. 00 1.00

Copper stearate 05 0.1 05 0.1 Di-salicylal ethylenediamine 0. 5 0. 5

- These stocks were cured for minutes at 40 lbs. steam pressure. They were tested by hanging samples in a Bierer Davis bomb at 70 C. and 300 lbs. oxygen pressure for 5 days and then determining their physical properties. The results ofthis test are given in Table I.

Table l- I "Icnsile T 11 M are 1 Completely deteriorated in 2-days. 7

It will be seen from this table that, whereas phenyl-b-naphthylamine is an extremely powerful antioxidant as shown by test A, it, is relatively ineffective when the oxidation is catalyzed by the presence of copper salts, tests B and C. It will be seen, however, that di-salicylal ethylene diamine overcomes the catalytic action of copper These stocks were cured for 45 minutes at 40 lbs. steam pressure. They were tested by charging samples in a Bierer Davis bomb at 70 C. and

300 lbs. oxygen pressure for 5 days and then determining their physical properties. The results of this test are given in the following Table IA:

Table IA Tensile Tensile Stock original gg Completely deteriorated.

3 These tests show that disalicylal-o-phenylene diamine is also a very effective compound in overcoming the catalytic effect of copper. Thus, while phenyl-b-naphthylamine is relatively ineifective in the presence of copper, the disalicylalo-phenylene diamine inhibits the action of copper and renders the phenyl-b-naphthylamlne effective. y

In order to show that this remarkable increase in effectiveness was due to overcoming the catalytic activity of the copper and not merely an additive effect due to the increased concentration of antioxidant, the following stocks were prepared:

Pale crepe 100 100 Zinc oxide 100 100 3 3 l 2 l 20 20 75 Phenyl-b-naplithylamine l. 00 1. 00 Di-salicylal ethylene diamine 0. 5

These stocks were cured for 45 minutes at 40 lbs. steam pressure. They were tested by the same oxygen bomb'test described above. The results of this test are given in Table II.

Table II T 11 tock $3, 55 .i ij

A 3,825 2, 550 B 3,900 2, s25

,IBrothers Publishing Company; 1036, p. 72).

.thiazole according to the disclosure of Uni These tests show thatthere is little or no imaz ma provement in the normal agingoi stocks containing phenyl b-naphthylamine when these .copper inhibitors are added ln the absencej'of copperpor its compounds which actlas catalyzers of oxidation.

In. order to show that the results oblbs, steam-pressure. They were tested by hanging samples ina Bierer-Davis bomb at '10 C.

and 300 lbs. oxygenl pressure for 3 days and then determining their physical properties. The results ofthis test are givenfin Table III. j I

Table III i "I ensile Tensile 3 days in m 7 original bomb 1 3, 375 Completely deteriorated. 3, 276 D0. 3, 275 Do, 3,1;75 Do.

when a rubber stock prepared similar those tested butomittinghoth the copper stea'rate and the antioxidant, it will likewise be completely deteriorated in 3 days. Accordingly, it appears tained are due to the combined actionoi the r compounds and not dueto either one alone. tests were made with the iollowinz stocks:

These stocks were curedior 45 minutes at 40 3 by the usualBierer Davis test. The results of thistest are given in Table IV. p

c Tablet? Tensile M1 one: egg;

egg 3.150

: C:I:I:IIII:I:III:3:122:11: i325 l,775

completelyldeteriorated. p

)It canwbe seen-lromxthis table that, in this testalso; where a butyraldehyde-aniline. condensation product was usedin place of phenyl-bnaphthylamine, the compounds are effective in overcoming thecatalytic .activityot --copper. r

1 Although tests have been. disclosed in which thesecompounds areused with either phenyl-bnaphthylamine or butyraldehyde-aniline as anti-L g oxidantspthey may be used with any or the that thesecompounds of our invention destroyf'or neutralizethe catalyticeiiect o! the copper-1 and its compounds and :thus permit the antioxidants to exertthelr usual action without interference irom the copper and its compounds.

These compounds are also eflective when used in conjunction with other known antioxidants.

is shown by tests made with the following a l stocks:

p A B r C.

Pale cm .100 I 100 100 Zinc oxide.. 10 p 10 10 biting--. 56 56 so Titonei i 75 75 r f 76 Stearlflacld..- 1.9 1.9 11.0 Heliosone"'.- 1.25 1.25 1.25 Salicylic acid 625 625 62 antioxidant) 1.25 x 1.25 1.25

Copper stearate .06 .05

Di-ealicylal-ethylene diamme .5

I Titone is-a reeniorcedlithopone containing about 16% titanium dioxide,60% barium sullate and 26% zincsulllde. "(See "Compounding Ingredients for. Rubber," copyright 1096, Bill BrothersPuhlishlng Company, p. r

Heliosonels the trade name of a specially selected group of wax materials. -,(Bee "Compounding Ingredients for Rubber," B

' Acrin is thetrade name of an accelerator n 1 tetramine benzyl "chloride and amen-mu hexamet y one I h b "if; Punt 1378M.

Antoxisthe trade name t e ut e tion product made acoordiugto United'states Patent 1,030,192.

condensatmn aone" hourcrise to 250 r. iollowedby a halt s e; [250? F. The properties or .these stocks were determined in the oxygen bomb 70 Thesestocks were cured in 30 1bs. air pressure 1 known antioxidants for rubber.

other compoundswhichmay be used asantioxidants along with the inhibitors for copper, are phenyl-a-naphthylamine, acetone-diphenylamine; acetone-aniline condensation products "and their polymerization. products, diphenyl ethylene-diamine, acetaldehyde-aniline, aldol-anaphthyiamine, 1310K} phenyl morpholine, di-

nunpyuuusaacn catechol borate, diphenylamine, diphenyl-p- ZDhQDYlBilB diamine, di-b-naphthyl p-phenylene diamine, 4(p-toluene sultonyl amino)? methyl diphenylamine, etc. i r a Examplesor other compounds; whichact as inhibitors ofthe'catalytic oxidation due to th 'presenceoi copper, are the following: i

Di-salicylal 1,6hexylene diamine m-saucylal 1241mm m-(many arocm) benaal) pr pylene di- .amine,

- Di-salicylal propylenediamine ,Dl-(MOH) sworn)- ben zal) ethylenedifamine 1Jl- (2(0H) benzal) dlethylene-triamine Di-salicylaltriethylene tetramine Di- (2(0H) 4-methyl benzaliyethylene diamine v r r eflectiye copper deactiv ators for inhibiting the action o! copper audits compounds on i oxidation of rubber may be made by condensina each of the following aldehydes with each of the following polyamines: i

" Aldehyde: Palyenlina OH benzaldehyde Methylene diamine 0H b-chlorobenzaldehyde Ethylenediamine 0H a li-dlbromobenzaldehyde. IQ-propylene diamine; 0H 3-nitrobenzaldeh de 1,3-propylenediamine OH d-methylbenzal eggde 1,1Mecylene dlamine 0B S-methoxy benzal dc Diethylene trlamine 4 0H; benzaldehyde Triethyiene ten-amine Odi 0H benzaldeh de Pentaerythrityl tetramlne 0H 3-cyanobenzai ehyde 1,2 -diamino cyolohexane. H 0H a-carbox bensaldehyds ifl-diaminobemlene O 'benzal ehydN-sulfonic 2,3-diaminopyridlne sci hthridlnc-L4, 220K; naphthaldehyded 4,6-diuninoq ollne 1 OH naphthaldehyde-I 1,8-diaminonaphthalene .Anthrol-Z-aldehyds-l lfldi'amino one 2 0H iluorenc aldslaigde-l .3,4-disn1inodi henyl 4 OH diphenylal M 9,10-dlamino throne a 011 I,4-toluylenadismine 2 1,8,di( H)-2,4-dia1dehydrobcn- 2:2'-diamlno diph enyl p M r 4:6-diamino phenanthrcne 4 0H quinolino-aldchyds-a 70 quinoline-aldshg dei f' 2 0 iurturyl aidshy Inall ot the tests disclosed; were" added r according tothe usual methods of Examples of incorporating before vulcanization. it should be pointed out, however, that they can be used as effectively by incorporating them into the rubber stock after, vulcanization by any of the well known processes of diffusion. These compounds can also be used effectively by introducing them -into 'latex, either natural or synthetic.

When-we refer to the catalytic effect of copper herein and in the claims,v it will be understood that werei'er to copperin the form of its salts or other catalytically active compounds as f well as in the form of the pure metal.

While we have disclosed the preferred embodiments of our invention, it will be readily ap-' parentto those skilled in'the art that many variations andmodiiications may be made therein without departing fromthe spirit of our invention. Accordingly, the scope of our invention is to be limited solely by the appended claims, construed as broadly as is permissible in view of the prior art.

We claim:

1. The method of retarding the deterioration of vulcanized rubber, due to the catalytic effect of copper in contact with the rubber, in the presence 5 of an antioxidant which is normally effective to materially retard'the deterioration of the vulcanized rubber due to light, heat and oxidation in the absence of copper but which is less efl'ective in the presence of copper, which comprises incorporating, in'the rubber in the proportion of from about 0.5% to about 1.0%, sufiicient to I inhibit the catalytic eifect of copper, a copper deactivator identical with the compound obtained by condensing 1 mole of a primary aliphatic .pclyamine solely with at least 2 moles oi. an

ortho hydroxy substituted aldehyde,aromatic in nature, so that not more than 1 mole of aldehyde 1 reacts for each primary amino group of the polyamine, said polyamine containing at least 40 two prfinary amino groups directly-attached to diiferent carbon atoms of the same open chain. 2. The method'of retarding the deterioration of vulcanized rubber due to the catalytic efiect of copper in contact with the rubber, in the presence of an antioxidant which is normally'efiective to materially retard the deterioration of, the vulcanized rubber due to light, heat and oxidation in the absence or copper but which is less 'eiIective in the presence of copper, which comby condensing 1 mole of a primary aliphatic polyamine solely with at least 2 moles of an ortho hydroxy substituted aromatic aldehyde, so that not more than 1 mole of aldehyde reacts for each primary amino group of the polyamine,

said polyamine containing at least two primary amino groups directly attached to difierent carbon atoms of the same open chain.

3. The method or retarding the deterioration of vulcanized rubber, due to the catalytic effect of copper in contact with the rubber, in the presence of an antioxidant which is normally efl'ectiye to materially retard the deterioration of the vul-- canized rubber due to light, heat and oxidation in the absence or copper but which is less .efiec-' tive in the presence of copper, which comprises incorporating in the rubber in the proportion of a I from about 0.5% to about 1.0%,suflicient to inhibit the catalytic eilect of copper, a copper deactivator identical with the compound obtained by condensing 1 mole of a primary aliphatic ..9. Vulcanized rubber polyamine solely with at least 2 moles of an ortho hydroxy substituted aromatic aldehyde, so that not more than 1 mole of aldehyde reacts for each primary amino group of the polyamine, said polyamine consisting of carbon, hydrogen and nitrogen and containing at least two primary amino groups directly attached to difierent carbon atoms of the same open chain, and said aldehyde consisting of the elements carbon, hydrogen and oxygen.

4. The method of retarding the deterioration of vulcanized rubber, due to the catalytic effect of copper in contact with the rubber, in the presence of an antioxidant which is normally effective to materially retard the deterioration of the vulcanizedirubber due to light, heat and oxidation in the absence of copper but which is less effective in the presence of copper, which comprises incorporating in the rubber in the proportion of from about 0.5% to about 1.0%, suflicient to inhibit the catalytic effect of copper, di-salicylal ethylene diamine.

, 5. The method of retarding the deterioration of vulcanized rubber, due to the catalytic eflect of copper-in contact with the rubber, in the presence of phenyl-b-naphthylamine, which comprises incorporating in the rubber in the proportion of from about 0.5% to about 1.0%,

suflicient to inhibit the catalytic effect of copper, di-salicylal ethylene diamine.

6. The method of retarding the deterioration of vulcanized rubber, due to the catalytic effect of copper in contact with the rubber, in the presence of a butyraldehyde-aniline antioxidant, which comprises incorporating in the rubber in the proportion of from about 0.5% to about 1.0%,

suflicient to inhibit the catalytic effect of copper,

-.terioration of the rubber due to light, heat and oxidation in the absence of copper but which is less efiective in the presence of copper, and from about 0.5% to about 1.0%, suflicient to inhibit the catalytic effect of copper, of a copper deactivator identical with the compound obtained by condensing 1 mole of a primary aliphatic polyamine solely with at least 2 moles of an ortho hydroxy substituted aldehyde, aromatic in nature, so that no more than 1 mole oi aldehyde reacts for each primary amino group of the polyamine,-said polyamine containing at least two primary amino groups directly attached to different carbon atoms of the same open chain.

having incorporated therein a small amount of an antioxidant which is normally effective to materially retard the deteriorationof the rubber due to light, heat and oxidationin the absence of copper but which is less'efiective in the presence of copper, EHdgfl'OHl about 0.5% to about 1.0%, suflicient to inhibit -the catalytic eiTect of copper, of acopper deo t r 2,285,259

, so that not more than 1 mole of aldehyde reacts for each primary amino group of the polyamine, said polyamine containing at least two primary amino groups directly attached to different carbon atoms of the same open chain.

. 10. Vulcanized rubber having incorporated therein a small amount ofanantioxidant which is normally effective tomaterially retard the deterioration ofthe rubberdue to light, heat and 1 oxidation in the absence of copper but which aromatic aldehyde, so that not more than 1 mole is less effective intthe presence of copper, and

from about 0.5%to about 1.0%, suflicient to inhibit'the catalytic efiect of copper, of a copper drogen and oxygen; i

11. Vulcanized rubber having incorporated therein a small amount of an antioxidant which is normally effective to materially retard the deterioration oi the rubberdue to light, heat and oxidation in the absence of copper but which is less eflectivein the presence of copper, and

from about 0.5% to about 1.0%, suflicient to inhibit the catalytic effect of copper, of a copper deactivator identical with the compound ohtained by condensing 1 mole of an alkylene diof aldehydereacts for each primary amino group of the amine said diamine containing the two primary amino groups directly attached to different carbon atoms of the same open chain, and said aldehyde consisting of the elements carbon, hydrogen and oxygen.

12. Vulcanized rubber having incorporated therein a small amount 01' an antioxidant which is normally effective to materially retard the deterioration or the rubber due to light, heat and oxidation in the absence of copper but which is :less eflective in the presence of copper, and from about 0.5% to about 1.0%, sufllcient toinhibit the catalytic effect of copper, of di-salicylal ethylene diamine. o i 13. Vulcanized rubber having incorporated therein a small amount of phenyl-b-naphthylamine, and from about 0.5% to about 1.0%, suflicient to inhibit the catalytic effect of copper, of di-salicylal ethylene diamine.

14. Vulcanized rubber having incorporated therein a small amount of a butyrald'ehyde-aniline antioxidant, and from about 0.5% to about 1.0%,-suflicient to inhibit the catalytic eflect of copper, of di-salicyle-i ethylene diamine.

15; Vulcanized rubber having incorporated therein a small amount of acetone-diphenylaminefand from about 0.5%to about 1.0%, sufficient to inhibit the catalytic efiect of copper, of di-salicylal ethylene diamine. a a

o FREDERICK B. DOWNING.

ARTHUR M. NEAL. x CHARLES J. PEDERSEN.

amine solely with 2 moles of an ortho hydroxy 

